It often is desirable to be able to precisely move a device relative to a fixed reference point. In some applications the desired movement is linear and the element that is used to cause the movement moves at right angles to the direction the device moves. In other applications the desired movement is rotational and it may be desired to rotate two devices with respect to a fixed reference around different axes. In this case, it often is desirable that the elements that are used to cause the movement are located near one another and are moved in a common direction.